A friend of Stieg Larsson's has revealed new details about the fourth book in the late Swedish author's bestselling Millennium series, which he said is set in a remote area of northern Canada in September.

"Did you know that 134 people live in Sachs Harbour, whose only contact with the world is a postal plane twice a week when the weather permits?" continued the author. "But there are 48,000 musk-ox and 80 different types of wild flowers that bloom during two weeks in early July, as well as an estimated 1,500 polar bears."

The three books in Larsson's Millennium series, The Girl with the Dragon Tattoo, The Girl Who Played with Fire and The Girl Who Kicked the Hornet's Nest, follow the crime-solving adventures of tattooed computer hacker Lisbeth Salander and journalist Mikael Blomkvist and have sold millions of copies around the world, as well as being made into a film.

Larsson's partner, Eva Gabrielsson, has previously admitted the existence of a fourth manuscript, telling the Observer earlier this year that "it's 200 pages long, and it has never been printed".

She has not revealed any details about its content, however, and according to the Associated Press Holmberg, who met Larsson at a science fiction convention in the 1970s, is the only other person to know what they contain.

Holmberg suggested that Larsson probably had a detailed outline of the plot of the story in his notes, so it would be possible for Gabrielsson, for example, to complete it. But Gabrielsson – who is embroiled in a dispute with Larsson's family over his estate – has previously said that as long as she is in possession of the draft, the pages will never be published.